The leading cause of lower back pain arises from rupture or degeneration of lumbar intervertebral discs. Pain in the lower extremities is caused by the compression of spinal nerve roots by a bulging disc, while lower back pain is caused by collapse of the disc and by the adverse effects of articulation weight through a damaged, unstable vertebral joint. One proposed method of managing these problems is to remove the problematic disc and replace it with a prosthetic disc that allows for the natural motion between the adjacent vertebrae (“a motion disc”).
U.S. Pat. No. 6,368,350 (“Erickson”) discloses a three-piece motion disc providing two articulation surfaces. The disc comprises a first piece having a curved surface, a second piece having a flat surface, and an intermediate piece having a corresponding curved articulation surface and a corresponding flat articulation surface.
Erickson does not teach providing a shock-absorbing component in addition to the articulating component between the prosthetic endplates.
U.S. Pat. No. 5,676,701 (“Yuan”) discloses, in one embodiment, a motion disc having a single articulation surface. This device includes a first component whose inner surface comprises a concave inner portion having a 360° circumference and a convex peripheral portion, and an opposing second component whose inner surface comprises a conforming convex inner portion and a convex peripheral portion. The convex/concave contours of the opposing inner portions forms a ball-and-socket design that allows unrestricted pivotal motion of the device, while the opposing convex peripheral contours allow flexion/extension bending motion in the range of about 20-30°.
However, Yuan does not teach providing a shock-absorbing component in addition to the articulating component between the prosthetic endplates.
U.S. Pat. No. 5,507,816 (“Bullivant”) discloses a three-piece motion disc providing two articulation interfaces and comprises an upper piece having a flat lower surface, a middle spacer having a flat upper surface and a convex lower surface, and a lower piece having a concave upper surface. The articulating convex and concave surfaces form an articulating interface that allows pivotal motion, while the flat surfaces form a translation interface that allows translational motion.
Bullivant does not teach providing a shock-absorbing component in addition to the articulating component between the prosthetic endplates.
U.S. Pat. No. 4,759,766 (“Buttner-Janz”) discloses a motion device comprising three components: an inferior endplate, a superior endplate, and a core having two articulation interfaces. Both the inferior and superior endplates are metal and have raised bosses with concave spherical surfaces in the center. The core is plastic and has convex surfaces on both the top and bottom which are surrounded by raised rims.
Buttner-Janz does not teach providing a shock-absorbing component in addition to the articulating component between the prosthetic endplates.
U.S. Pat. No. 5,314,477 (“Marnay”) discloses a device having a single articulation interface and comprises three components: an inferior endplate, a superior endplate, and a plastic insert. The inferior endplate functions as a baseplate and has a sidewall forming an open ended channel for reception of the insert. The inner surface of the inferior endplate provides only stationary support for the insert and does not have a motion surface. Since the plastic insert is designed to be locked securely into place within the inferior endplate, the inferior surface of the insert is not a motion surface. The superior surface of the insert includes articulation surface for articulation with the superior endplate. The superior endplate has an inferior articulation surface that articulates with the superior motion surface of the plastic insert, and a superior surface designed for attachment to a vertebral endplate.
Marnay does not teach providing a shock-absorbing component in addition to the articulating component between the prosthetic endplates.
French Published Patent Application No. 2,730,159 (“Germain”) discloses a motion disc in which the core member has one convex and concave surface. Germain further teaches that the radius of the upper curved surface (3a) of the core member is less than the radius of the lower curved surface (3b) of the core member.
Germain does not teach providing a shock-absorbing component in addition to the articulating component between the prosthetic endplates.
U.S. Pat. No. 5,824,094 (“Serhan”) discloses a cushion-type motion disc wherein a rubber core is sandwiched between two metal prosthetic endplates. The rubber core provides a shock-absorbing effect and so mimics the natural response to axial load. However, the rubber core was found to experience high shear stresses in use.
U.S. Pat. No. 6,579,321 (“Gordon I”) discloses an implantable disc that comprises a support ball that acts as a pivot point. The support ball is of the constrained type and does not represent a mobile, free-floating type of core since the core is fixed and the motion of the disc occurs about a fixed center (the center of the ball). Additionally, the support ball has only a single contact surface.
U.S. Pat. No. 6,964,686, US Published Patent Applications US20050027363, US20050043804, US20050234553, and WO2005039455 (“Gordon II”) discloses a disc that comprises a first piece having a curved surface, a second piece having a flat surface, an intermediate piece having a corresponding curved articulation surface and a corresponding flat articulation surface, and a helical spring encasing the device. However, Gordon does not teach providing an intermediate piece (the core) having opposed convex surfaces. By not doing so, Gordon fails to recognize the advantages provided by a “floating” mobile core. It is believed that a free motion or “floating” core provides a better way to duplicate the instantaneous articulating center of rotation of the natural disc.
U.S. Pat. Nos. 5,989,291 and 6,669,731 and US Published Patent Applications US20020111681, US20020111683, US20030040802, and US20030074073 (“Ralph”) disclose certain devices that provide rotational motion to the functional spinal unit by means of a spherical ball articulating in a corresponding socket, while translational motion about the vertical axis is allowed to a certain degree via at least one Belleville washer or similar feature. Ralph did not consider utilizing a mobile core and instead used a fixed core.
PCT Patent Publication No. WO2004016217 (“Gerber”) discloses a multi-piece device having one or more helical springs with one or both ends articulating via a curved surface. This type of device does not present a combination of a free floating, mobile, convex-convex core and a helical shock absorber.
US Published Patent Application No. 20040073310 (“Moumene”) discloses an intervertebral disc having two opposite endplates, a central articulating core, and a peripheral shock absorber. The peripheral shock absorber is not in the form of a helix.
US Published Patent Application No. 20050065610 (“Pisharodi”) discloses a rotating, spring-loaded implant that only provides for pre-loading elements forming the arthroplasty device.
US Published Patent Application No. 20050228500 (“Kim”) discloses upper and lower endplates separated by a compressive core member, wherein the device stiffness is controlled independently by adjusting the components of the disc. A helical shock absorber is disclosed as being located inside the articulating core.
US Published Patent Application No 20050165486 (“Trieu”) discloses a device that resists at least one predetermined directional motion between first and second components. However, Trieu does not teach providing a helical shock absorber in addition to the articulating component between the prosthetic endplates.
US Published Patent Application No. 2006/0200242 (“Rothman I”) discloses an intervertebral stabilizer including a first surface operable to engage an endplate of a first vertebral bone of a spine; a second surface spaced apart from the first surface and operable to engage an endplate of an adjacent second vertebral bone of the spine; and a spring element between the first and second surfaces and operable to provide a reactive force in response to compression loads from the first and second vertebral bones, wherein a cross-sectional profile taken through the spring is hourglass shaped.
US Published Patent Application No. 2006/0217809 (“Albert I”) discloses an intervertebral stabilizer including a first plate member operable to engage an endplate of a first vertebral bone of a spine; a second plate member spaced apart from the first plate member and operable to engage an endplate of an adjacent second vertebral bone of the spine; a ball element depending from the first plate member; and a socket element depending from the second plate member, wherein at least one of the ball and socket elements include one or more keyed surfaces such that (i) an assembly function is obtained in which the ball element may at least one of be received into, and removed from, the socket element in one or more first articulation positions of the first and second plate members; and (ii) a capture function is obtained in which the ball element may at least one of not be received into, and not be removed from, the socket element in one or more second articulation positions of the first and second plate members.
US Published Patent Application No. 2006/0200241 (“Rothman II”) discloses an intervertebral stabilizer including a first surface operable to engage an endplate of a first vertebral bone of a spine, a second surface spaced apart from the first surface and operable to engage an endplate of an adjacent second vertebral bone of the spine; a spring element between the first and second surfaces and operable to provide a reactive force in response to compression loads from the first and second vertebral bones, wherein a cross-sectional profile taken through the surfaces is hourglass shaped.
US Published Patent Application No. 2006/0200240 (“Rothman III”) discloses a lumbar intervertebral stabilizer for a lumbar region of a spine, including a first surface operable to engage an endplate of a first vertebral bone of a spine; a second surface spaced apart from the first surface and operable to engage an endplate of an adjacent second vertebral bone of the spine; a spring element including at least one of (i) a helical wound spring; and (ii) a hollow body having at least one slit forming a plurality of annular circumferential helical coils, the spring element being disposed between the first and second surfaces and being operable to provide a reactive force in response to compression loads from the first and second vertebral bones, wherein at least some diameters of the respective turns of the helical coils differ.
US Published Patent Application No. 2006/0200239 (“Rothman IV”) discloses a posterior intervertebral stabilizer including a first stabilizing element having (i) a first surface operable to engage an endplate of a first vertebral bone of a spine, and (ii) a second surface spaced apart from the first surface and operable to engage an endplate of an adjacent second vertebral bone of the spine; a second stabilizing element having (i) a first surface operable to engage an endplate of the first vertebral bone of the spine, and (ii) a second surface spaced apart from the first surface and operable to engage an endplate of the adjacent second vertebral bone of the spine, each including helical coils disposed between the respective first and second surfaces of the first and second stabilizing elements, each operable to provide a reactive force in response to compression loads from the first and second vertebral bones, wherein at least some diameters of respective turns of the respective helical coils differ.
US Published Patent Application No. 2003/0220691 (“Songer”) discloses a motion disc having an upper endplate, a lower endplate, an articulating core therebetween and a peripheral shock absorber disposed around the core. See FIG. 11G.